The present invention relates to an electromagnetic shielding structure for connecting electric wires or cables to input and output terminals of a motor and general electronic equipment mounted on, especially, an electric car.
In the case that electric wires or cables are connected to input and output terminals of a motor mounted on an electric car, a grounding structure, in which a shielding member is grounded by being connected to a structure-attached body such as a casing for accommodating the motor, is employed so as to prevent leakage of electromagnetic waves from the wires or cables to the outside, and conversely, so as to protect the motor from the influence of external electromagnetic waves received from the outside.
An example of an electromagnetic shielding structure of such a kind is a connector for a shielding cable, which is shown in FIG. 8 and described in Japanese Utility Model Publication Hei. 6-23179. In this connector, a plurality of pin terminals 3 are held by a terminal holding member 2 provided in a metallic cylindrical shell 1. A shielding cable 4 to be connected to this connector is constructed by twisting a plurality of insulated cores 5, which are constituted by conductors 5a, such as copper wires, coated with insulating materials 5b, and then putting a metallic braid 6 around the twisted and insulated cores 5 as a shielding sheet, and further covering the metallic braid 6 with a sheath 7 serving as an outermost layer. The conductors 5a are exposed by peeling such a cable terminal. Each of such conductors 5a is connected to a corresponding one of pin terminals 3.
The sheath 7 serving as the outermost layer of the cable terminal is peeled, so that the braid 6 is made uncovered. Then, this exposed braid 6 is covered with a cylindrical metallic net 8. Moreover, this metallic net 8 is covered with a heat shrinkable tube 9. Thus, the metallic net 8 is connected and fixed to both the connector-side shell 1 and the cable-side braid 6 by a contractional pressure obtained by heating this heat shrinkable tube 9. Consequently, the cable-side braid 6 is fixed to the connector-side shell 1 in a state, in which the braid 6 and the shell 1 are electrically conducted to each other, to thereby provide electromagnetic shielding.
Meanwhile, this magnetic shielding structure shown in FIG. 8 and described in the aforementioned official gazette has encountered the following problems.
One of the problems is that the metallic net 8 is pressed own only by a pushing force due to shrinkage of the heat shrinkable tube 9, which is caused by applying heat thereto, and the connector-side shell 1 is brought into contact with the cable-side braid 6 to thereby put the shell 1 and the braid 6 into an electrically conducted state, that thus, the braid 6 is insufficiently pressed against the shell 1, that shield resistance is unstable, that electromagnetic shielding is not effectively provided, and that the reliability of the connection therebetween cannot be expected.
Further, another of the problems is that when the heat shrinkable tube 9 is damaged, for example, tore, there is a fear that the metallic net 8 providing the connection between the shell 1 and the braid 6 and the contact therebetween is detached to thereby cause a state in which the shell 1 is not electrically conducted to the braid 6.
Accordingly, an object of the invention is to provide an electromagnetic shielding structure enabled to effectively provide electromagnetic shielding by enhancing the reliability of the connection.
In order to solve the aforesaid object, the invention is characterized by having the following arrangement.
(1) An electromagnetic shielding structure comprising:
an electrically conductive grounded and structure-attached body;
an insulating housing, through which an electric wire is passed, watertightly fitted into and held by the structure-attached body;
an elastic sealing member fitted into and held by the housing and being in watertight contact with an outer periphery of the wire;
a flexible and electrically conductive shielding sheet for covering the wire;
a shielding terminal electrically conducted with the structure-attached body in a state in which an outer surface thereof is covered by and contacted with an end part of a skirt portion of the shielding sheet;
a band-like clamp tightly fasten the end part of the skirt portion of the shielding sheet from the outside thereof and to cause the end part of the skirt portion to be in intimate contact with the outer surface of the shielding terminal; and
a protector for covering the clamp from the outside thereof and for accommodating and protecting the structure-attached body, the housing, the elastic sealing member, the shielding sheet, the shielding terminal, and the clamp.
(2) The electromagnetic shielding structure according to (1), wherein
the housing includes front and rear housing portions holding the elastic sealing member from front and rear sides thereof, respectively, to bring a part of an outer circumferential surface of the elastic sealing member into intimate contact with the structure-attached body, and
the front housing is engaged with a metal terminal attached to an end portion of the wire.
(3) The electromagnetic shielding structure according to (1), wherein the elastic sealing member is closed by an electrically conductive cover from one side thereof, and a stopper is provided to the housing to prevent a metal terminal attached to the wire from moving.
(4) The electromagnetic shielding structure according to (1), wherein an inner portion of the shield sheet is welded to the shielding terminal by performing spot-welding on the clamp.
(5) The electromagnetic shielding structure according to (1), wherein end parts of skirt portions of the shielding terminal and the protector are together connected to the structure-attached body by bolt.
With the aforementioned configuration, in the case that the electrically conductive shielding sheet that covers the full length of the electric wire, when an electromagnetic shield is electrically conducted by connecting an end part of a skirt portion of this braid to the structure-attached body B, the end part of the skirt portion of this braid is inserted into between the shielding terminal and the clamp and fixed to therebetween. Thus, the end part of the skirt portion of the braid can be reliably and firmly connected to the structure-attached body. The clamp is shaped like a band. Thus, the end part of the skirt portion of the braid is tightly fastened, so that sufficient contact is obtained over the entire circumference thereof. Moreover, this structure can completely eliminate the fear that the braid may be tore. Consequently, it can be expected that effective electromagnetic shielding effects are obtained. Further, stable electric characteristics are obtained, so that the reliability of the connection therebetween can be enhanced.
In this case, the entire electromagnetic shielding structure portion is accommodated in the protector. Thus, the first magnetic shielding structure is effective in protecting the electrically shielding sheet, such as the braid, without exposing the shielding sheet to the outside.
According to the invention, the housing is divided into the front portion and the rear portion. Thus, the entire elastic sealing member other than the parts, which are fitted into the structure-attached body in such a manner as to be watertightly in intimate contact therewith, can be held and protected in the front housing and the rear housing. Moreover, this electromagnetic shielding structure is effective in preventing an occurrence of misalignment of the axis of the elastic shielding member.
According to the invention, when the housing is closed by the electrically conductive cover member, this electromagnetic shielding structure is effective in preventing an occurrence of misalignment of the axis of the wire passed through and held in the housing by way of the elastic sealing member. This electromagnetic shielding structure is also effective in preventing the elastic shielding member from slipping off. Furthermore, the movement in the direction of the axis and the slip-off of the metal terminal fitting is regulated and prevented by the stopper provided in the housing.
According to the invention, the electrically conductive band-like clamp is spot-welded. Thus, the entire circumference of the end part of the skirt portion of the braid serving as the electrically conductive shielding sheet is brought into rigid contact with the shield terminal. Thus, there are no fears that the contact force may be insufficient that the braid may be tore. Reliable shielding and conducting between the structure-attached body and the shielding terminal are achieved. Consequently, stable electromagnetic-shielding effects can be obtained.
According to the invention, more stable and reliable shielding and conducting of the portion for connecting electric wires or cables to the input and output terminals can be obtained by fastening together the shielding terminal and the protector to the structure-attached body by bolts.